1. Field of the Invention
This invention relates to improvements in or relating to a multi-directional sound signal recording and/or reproducing system, commonly known under the name of a discrete 4 channel stereo system, which is designed for multiplex recording of a plurality of main channel signals and a plurality of carrier modulated type sub-channel signals in a single sound groove of a record and/or reproducing of the recorded signals therefrom.
2. Description of the Prior Art
One of such types of systems heretofore employed in the art is a "Universal Matrix system" (hereinafter referred to as the UM system) proposed by Duane H. Cooper, one of the present inventors.
The UM system is excellent in compatibility with a conventional mono-aural system and an ordinary two channel stereo system and capable of reproducing of sound sources with high fidelity, ensures the locations of sound images to be distinct and permits freedom of disposition of speakers; and hence is very advantageous in practical use.
However, the multi-directional sound system such as the UM system which employs a carrier sub-channel signal encounters the following problems.
One of the problems is that since the pass band of the carrier sub-channel signal is limited for narrowing a required frequency band of the system as a whole, clipping distortion is caused at the time of overmodulation.
Another problem is the generation of beat distortion in a demodulated sub-channel signal due to cross-talk between the carrier sub-carrier channels in the recording system and, mainly in the reproducing system.
Still another problem is the generation of cross-talk from the main channel signal to the sub-channel signal (hereinafter referred to as the Up-talk) which is caused by a tracking error and tracing distortion in the reproducing system.